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Shade Tree Pimpin'
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1,123 Posts
Discussion Starter #1
i have a serious missfire problem and it throws the random missfire code it happens in the moring when i first start it and also when i first drive it in the moring it misses really bad, i have a 2001 blazer with the hyperteck 93 octan program instaled with a msd blasster and wire, autolite spark plugs (not platinum), and it has abour 60 k on it
 

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Early Member
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3,167 Posts
I am checking....




Ok. Check your sparkplug gap. Make sure your plug wires are on the correct cylinder. Have you changed the fuel filter?
 

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Early Member
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3,167 Posts
One more thing. A lot of people are not on this forum until later in the day.
 

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Road Race/Auto X S10
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3,828 Posts
Try installing your stock coil.
 

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29 Posts
I had the same problem. There is a thread on here that talks about that same problem. GM issued a TSB about this a few years back. The Pintle needle in your CMFI becomes clogged over time due to deposits, it will stick in the open position, allowing fuel to drip, and causing cylinders to misfire. The procedure calls for trying to clean, and if it cant be cleaned, then replace the CMFI (CPI). What I did was run my tank down to a quarter tank of gas, and add a whole bottle of Injector cleaner. Once that had run through, i made sure the gas was just a little over empty, and added just a little sea foam (like a cup or so). I ran that through, and then just filled the tank like normal. I havent had the 0300 random missfire code since. Its also not having the misfire and running like a log truck on the cold mornings. Hope this helps.
 

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Shade Tree Pimpin'
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1,123 Posts
Discussion Starter #7
what is sea foam and what am i cleaning out what is the CMFI
 

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Registered
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12 Posts
You can PU Seafoam at O'Reilly Auto Parts. Probably can get at other auto supply houses also. Is like $9.00 for a 14oz bottle.
 

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Early Member
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3,167 Posts
CMFI is Central Multiport Fuel Injection, aka CPI. And I think your truck is SEFI and not CPI.
 

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Clean N' Dark
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1,921 Posts
If it only happens in the morning, you need to replace your cap and rotor.

What you are getting is condensation in the cap arcing and mis-firing the spark. When the truck warms up, the heat drives out the moisture.

All times this has happened to me, I replaced the cap and rotor and all was well.
 
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